Chicago Board of Trade (CBOT) grains futures closed lower over the trade week which ended Aug. 11, mostly on National Agricultural Statistics Service's (NASS) bearish U.S crop yield.

The most active corn contract for December delivery fell 6.25 cents weekly, or 1.67 percent, to 3.7475 dollars per bushel. September wheat delivery dropped 15.5 cents weekly, or 3.53 percent, to 4.3925 dollars per bushel. November soybeans fell 11.75 cents weekly, or 1.24 percent, to 9.45 dollars per bushel.

December corn fell 6.25 cents, which was entirely a function of NASS's bearish U.S. yield surprise. Friday's trade was moderately higher, and there's a general consensus that NASS's first year weight guess is too high, to a degree that is yet to be determined.

Market analysts maintains a U.S. corn yield of 166 bushels per acre, but there's evidence to suggest an even lower number by the October or November crop reports.

South American corn exports continue to dominate world trade, but demand has rallied Brazilian and Argentine basis bids substantially. It's far too late to turn bearish South American cash prices.

Wheat futures again closed sharply lower on a bearish August World Agricultural Supply and Demand Estimates (WASDE) report and ongoing fund liquidation.

An upward revision was fully expected to Black Sea production, but the United States Department of Agriculture (USDA) in its report this week raised combined Ukraine and Russian wheat production to 7.5 million tons, which no doubt exceeded expectations and also pushed major exporter stocks/use noticeably higher.

Soybeans were on both sides of unchanged through the week and finished lower. Short covering ahead of the USDA's August Crop Report offered support in the first half of the week, while a much larger than expected yield estimate sent the market sharply lower on Thursday.

The trade had been positioned for a U.S. soybean yield around 47 bushels per acre, while NASS estimated a yield of 49.4 bushels per acre.

Based on much weaker conditions and some crop analyst assessment of Midwest fields, most traders' view is that the August USDA yield estimate could be the highest of the year.

Crop ratings are expected to be unchanged to one percent lower on Monday as cool temps in the last week have helped offset limited rainfall. However, much of the Midwest is in dire need of rain, while the weather models projected limited rains and building heat in the next 10 days.